Number of ways to go up and down n stairs, with fewer than 4 stairs at a time, stepping on each stair at least once.

A287898

Number of ways to go up and down n stairs, with fewer than 4 stairs at a time, stepping on each stair at least once.

Terms

    a(0) =1a(1) =3a(2) =9a(3) =27a(4) =79a(5) =233a(6) =687a(7) =2025a(8) =5969a(9) =17595a(10) =51865a(11) =152883a(12) =450655a(13) =1328401a(14) =3915743a(15) =11542481a(16) =34023905a(17) =100292659a(18) =295633833a(19) =871443275a(20) =2568763439a(21) =7571973753a(22) =22319994767a(23) =65792907193a(24) =193938514865a(25) =571674807403

External references